feat: add AI-powered visual regression testing infrastructure

- Add docker-compose.web-testing.yml with vlmkit service
- Add 5 test scripts: capture, compare, pipeline, console-monitor, link-checker
- Add vrt.config.json with 3 viewports + maskSelectors
- Add package.json with @mizchi/vlmkit and Node >=24
- Add tests/README.md with VRT documentation
- Update .gitignore for test artifacts

Based on APAW issue #144 / milestone #106

tests/scripts/link-checker.js

@@ -0,0 +1,83 @@
+const { chromium } = require('playwright');
+const fs = require('fs');
+const path = require('path');
+
+const TARGET_URL = process.env.TARGET_URL;
+const PAGES = (process.env.PAGES || '/').split(',').map(p => p.trim());
+const REPORTS_DIR = process.env.REPORTS_DIR || './reports';
+
+async function collectLinks(page, pagePath) {
+  const fullUrl = `${TARGET_URL}${pagePath}`;
+  await page.goto(fullUrl, { waitUntil: 'networkidle', timeout: 30000 });
+  return page.evaluate(() => Array.from(document.querySelectorAll('a[href]'))
+    .map(a => a.href));
+}
+
+async function checkLink(context, url) {
+  try {
+    const resp = await context.request.fetch(url, { method: 'HEAD', timeout: 15000 });
+    return { url, status: resp.status(), ok: resp.ok() };
+  } catch (err) {
+    return { url, status: 0, ok: false, error: err.message };
+  }
+}
+
+async function main() {
+  if (!TARGET_URL) {
+    console.error('TARGET_URL environment variable is required');
+    process.exit(1);
+  }
+
+  const browser = await chromium.launch({ headless: true });
+  const context = await browser.newContext();
+  const results = [];
+
+  try {
+    for (const pagePath of PAGES) {
+      const page = await context.newPage();
+      try {
+        const links = await collectLinks(page, pagePath);
+        await page.close();
+        const checked = [];
+        for (const url of [...new Set(links)]) {
+          if (url.startsWith('mailto:') || url.startsWith('tel:')) continue;
+          checked.push(await checkLink(context, url));
+        }
+        const broken = checked.filter(c => !c.ok);
+        results.push({ pagePath, total: checked.length, broken: broken.length, brokenLinks: broken });
+        console.log(`${pagePath}: ${checked.length} links, ${broken.length} broken`);
+      } catch (err) {
+        results.push({ pagePath, error: err.message, total: 0, broken: 0, brokenLinks: [] });
+        console.error(`Failed ${pagePath}: ${err.message}`);
+      } finally {
+        await page.close().catch(() => {});
+      }
+    }
+  } finally {
+    await browser.close();
+  }
+
+  const totalBroken = results.reduce((s, r) => s + r.broken, 0);
+  const report = {
+    timestamp: new Date().toISOString(),
+    targetUrl: TARGET_URL,
+    pages: PAGES,
+    summary: { totalPages: results.length, totalBroken, hasBroken: totalBroken > 0 },
+    results,
+  };
+
+  fs.mkdirSync(REPORTS_DIR, { recursive: true });
+  const reportPath = path.join(REPORTS_DIR, 'link-check-report.json');
+  fs.writeFileSync(reportPath, JSON.stringify(report, null, 2));
+  console.log(`Report saved to ${reportPath}`);
+
+  if (totalBroken > 0) {
+    console.error(`Found ${totalBroken} broken links`);
+    process.exit(1);
+  }
+}
+
+main().catch(err => {
+  console.error('Fatal error:', err);
+  process.exit(1);
+});